Synthesis and in situ core reorganization of smart polymers

A smart poly(ethylene oxide) polymer containing two thermally reversible groups located at the chain center (F2-PEO) was synthesized by a maleimide-furan (MF) [4 + 2] Diels-Alder (DA) reaction between one bis[(furan-2-yl)methyl] terephthalate (F2) and two maleimide-terminated poly(ethylene glycol) methyl ethers (MI-PEOs). MF adducts underwent retro-DA (rDA) addition at a higher temperature, and the maleimide-anthracene (MA) addition reaction could occur simultaneously. Therefore, when F2-PEO and bis((anthracen-10-yl)methyl) succinate (AN2) were refluxed in toluene for 48 h, the cores of F2-PEOs were replaced with the MA adducts in situ to give new polymers AN2-PEOs. Moreover, when F2-PEOs were mixed with the molecules containing four anthracene units (AN4), the rDA reaction of the MF adducts and the MA addition reactions occurred simultaneously, generating four-arm star PEOs. The core reorganization of polymers has been confirmed by SEC, UV, 1H NMR, and MALDI-TOF mass spectra.